Oxide magnetic materials

ABSTRACT

Manganese-zinc ferrites are provided consisting essentially of manganese oxide, zinc oxide and iron oxide and small but effective amount of stannic oxide and lithium oxide ranging up to about 3.2 percent by weight of stannic acid and up to about 0.125 percent by weight of lithium oxide.

llnited States Patent Sugano et all.

1 51 Mar. 28, 1972 OXIDE MAGNETIC MATERIALS lnventors: lzuru Sugano; Tsuneo Akashi; Tetsujin Matsubara; Yoshihiro Kenmoku; Taneaki Okuda, all of Tokyo, Japan Assignee: Nippon Electric Company, Limited,

Tokyo, Japan Filed: Oct. 29, 1969 Appl. No.: 872,094

Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 3,415,751 12/1968 Hirota et a] ..252/62.59 3,492,236 1/1970 Ross ..252/62.59

Primary Examiner-Daniel E. Wyman Assistant Examiner-J. Cooper Attorney-Sandoe, Hopgood and Calimafde [57] ABSTRACT Manganese-zinc ferrites are provided consisting essentially of manganese oxide, zinc oxide and iron oxide and small but effective amount of stannic oxide and lithium oxide ranging up to about 3.2 percent by weight of stannic acid and up to about 0.125 percent by weight of lithium oxide.

3 Claims, 18 Drawing Figures OXIDE MAGNETIC MATERIALS This invention relates to new oxide magnetic materials with greatly improved quality and hysteresis loss factors.

Manganese-zinc ferrites have found extensive applications as excellent soft magnetic materials for communications use in the frequency band near 100 KHZ. and various improvements in magnetic properties have been attempted to cope with their diversified application fields. In keeping with the present-day rapid progress of communications equipment, miniaturization and high performance of magnetic cores have been in great demand, with the result that improvements in material and performance of ferrites themselves have become an important problem. 7

The addition of one, two or more kinds of additive or modifying agents to the manganese-zinc ferrite composition in a number of combinations has been attempted for the purpose of improving both quality and hysteresis loss factors. However, manganese-zinc ferrites with quality factors (tan 8/p.) and hysteresis loss factors (h10) less than 2 X 10 and at 100 kl-lz., respectively, have hitherto not been attainable.

The quality factor and the hysteresis loss factor are defined according to the following equation:

R/wL tan S/ are h .3/1000) (L/V') I wherein:

R effective resistance of core in ohms L inductance of coil in henrys u initial permeability of core e effective permeability of core V effective volume of core in cubic centimeters I measuring current in amperes it is an object of this invention to provide ferrites of the system MnO--ZnO-Fe,0 having markedly improved quality and hysteresis loss factors.

Other objects of the invention will more clearly appear from the following disclosure and the accompanying drawing, wherein:

FIGS. 1 to 18 illustrate the manner in which the magnetic properties of the ferrites are improved by this invention.

The present invention resides in the addition of stannic oxide (SnO and lithium oxide (Li O), in combination to the manganese-zinc ferrite composition in amounts that effectively improves the loss characreristics of the ferrites, i.e., both the quality factor and the hysteresis loss factor.

Before describing in detail the subject matter of this invention, it will be noted hereinafter from Example 1 that a remarkable effect can be obtained for improvements in both the quality and the hysteresis loss factors when a compound of tin and a compound of lithium are added together to a manganese-zinc ferrite having a basic composition containing 55.9 mol percent Fe O 38.0 mol percent MnO, and 6.1 mol percent ZnO as the main constituents so that the additives may ultimately take the form of SD02 and U 0.

ln Examples 2 through 6 also appearing hereinafter, it will be observed that the effect of combined SnO, and Li,O as additive agents remains substantially unchanged for manganesezinc ferrites having different basic compositions from that mentioned in Example 1, and that there are optimum amounts of the additive agents and the allowable limits therefor for each basic ferrite composition.

In Example 7, it will be noted that the effect of the presence of SnO, and U 0 in the ferrite composition is markedly noticeable even when a special heat treatment is applied for improving magnetic properties as disclosed in Japanese patent application, No. 62961/1967.

Finally, in Example 8, it will also be noted that the effect of the addition of Sn0 and LL 0 per se remains substantially unchanged even when another combination of additives, such as CaO and $0,, is present in varying amounts in the manganese-zinc ferrite composition.

It will be understood, all the specimens used in the examples that follow were prepared according to the known sintering ferrite manufacturing method.

in producing the ferrite composition, iron oxide, manganese carbonate, zinc oxide, calcium oxide, and silicon oxide, together with the essential additive agents of this invention, i.e., stannic oxide and lithium carbonate, are individually weighed so as to obtain a predetermined composition and these compounds were mixed and pulverized for about 60 hours in a ball-mill using alcohol as a dispersion medium, followed by presintering the mixture for about 4 hours at about 800C, pressing into a desired shape, firing for about 8 hours at about 1180C in a nitrogen atmosphere containing 0.4 percent oxygen and then cooling. During cooling, the oxygen content in the nitrogen atmosphere is controlled.

All of the specimens in Examples 1 through 7 contained 0.06 wt. percent of calcium oxide and 0.02 wt. percent of silicon oxide, although not explicitly mentioned in each case. The effectiveness of the invention will be best understood by reference to the following examples.

EXAMPLE 1 FIGS. 1 and 2 in combination demonstrate that the effect of U 0 and Sn0 added together to a manganese-zinc ferrite having a basic composition of 38.0 mol percent MnO, 6.10 mol percent ZnO, and 55.90 mol percent Fe,,0 is excellent insofar as improvements in the loss characteristics tan tS/p. and h are concerned. An inspection of these graphs readily reveals the following: Both tan 8/ and h are markedly improved by the addition of SnO and Li O in small but effective amounts ranging from:

0.6 wt. Sn0 2.7 wt. and 0 wt. Li O s 0.1 wt. Markedly improved materials meeting the two conditions tan Sly. 1.0 X 10 and h 3 at KHz. heretofore not realized can be obtained.

EXAMPLE 2 FIGS. 3 and 4 illustrate in combination the effect of Li,0 and SnO, added together to a manganese-zinc ferrite having a basic composition of 36.0 mol percent MnO, 8.8 mol percent ZnO, and 55.2 mol percent re o, As is apparent, very good oxide magnetic materials meeting the two conditions tan ti/u 1.0 X 10", and h 3 can be obtained by the addition of small but effective amounts of from 0.6 to 2.7 wt. percent SnO and from 0.01 to 0.1 wt. percent Li O. Such markedly improved magnetic properties have heretofore not been realized.

EXAMPLE 3 FIGS. 5 and 6 illustrate in combination the effect of Li,0 and SnO added together to a manganese-zinc ferrite having a basic composition of 36.0 mol percent MnO, 9.5 mol percent ZnO, and 54.5 mol percent R 0 As is apparent from these graphs, excellent oxide magnetic materials meeting the two conditions tan 6/ 1.0 X 10', and h 3 at 100 KHz. are obtained by the addition of small but effective amounts of SnO, and U 0 in the ranges expressed as 2.0 wt.% E SnO- 3.2 wt.% 0.0 1wt.% Li O 5 0.06 wt.

EXAMPLE 4 FIGS. 7 and 8 indicate in combination the effect of U 0 and Sn0 added together to a manganese-zinc ferrite having a basic composition of 34.0 mol percent MnO, 1 1.60 mol percent ZnO, and 54.4 mol percent Fe O As is apparent from these graphs, the loss characteristics of the ferrites can be markedly improved by the addition of small but effective amounts of SnO and U 0 expressed as 0.8 wt.% Sn0 2.3 wt.% 0 wt.% Li 0.07 wt.% and excellent oxide magnetic materials meeting the two conditions, tan 8],; l.2'X 10' and h 4, at 100 KHz. can be ob tained.

These loss characteristics have not heretofore been realized by any known method.

EXAMPLE 5 FIGS. 9 and 10 indicate in combination the effect of SnO and Li o added together to a manganese-zinc ferrite having a basic composition of 34.0 mol percent MnO, 10.75 mol percent ZnO, and 55.25 mol percent Fe O As is apparent from these graphs, excellent oxide magnetic materials meeting the two conditions tan 8/11. 1.2 X 10 and h 4, heretofore have not been realized by known methods, can be obtained by the addition of small but effective amounts of SnO and U expressed as 0 wt. SnO a 1.4 wt.% 0 wt. Li O 0.06 wt.%

EXAMPLE 6 FIGS. 11 and 12 indicate in combination the effect of SnO and Li O added together to a manganese-zinc ferrite having a basic composition of 32.0 mol percent MnO, 13.15 mol percent ZnO, and 54.85 mol percent Fe O As is apparent, excellent oxide magnetic materials meeting the two conditions, tan Blp. 1.3 X l0 and h at 100 KHz., can be obtained by the addition of small but effective amounts of SnO and U 0 expressed as 0.4 wt.% E SnO 1.1 wt.% 0.01 wt.% Li O 0.05 wt.%

As a result of conducting many experiments under various sintering conditions (such as disclosed in Japanese patent application No. 5507/1967 or when the sintering atmosphere is ca sed to change) other than that mentioned in the foregoing examples-that is, sintering for 8 hours at 1180C in a nitrogen atmosphere containing 0.4 percent oxygen, the effect of combined stannic oxide and lithium oxide could be manifestly observed, although optimum composition ratios of Sn0 to Li O were subject to slight change.

The effect of the addition of SnO and Li O was substantially unaffected even if the sintered body was subjected to a heat treatment intended for improvements in magnetic properties such as disclosed in Japanese patent application No. 62961/1967.

An example for this is shown in Example 7 that follows.

EXAMPLE 7 FIGS. 13 and 14 illustrate respectively improvements in the loss characteristics tan 8/11. and h of specimens of a ferrite having the same composition as in Example 1, i.e., MnOzZ- nOzFe o 38:61:55.9 mol percent and containing Li O and SnO as additive agents, the specimens being prepared, after sintering, by subjecting to a heat treatment for 32 hours at 250C.

An inspection of these graphs readily reveals a marked degree of improvements in the loss characteristics tan 8/pt and h due to the addition of small but effective amounts of SnO and Li O in the following ranges:

Thus excellent magnetic materials meeting the two conditions tan 8/ 0.8 X and h 3 at 100 KHz. can be obtained.

The manganese-zinc ferrites used in this example contained 0.06 wt. percent CaO and 0.02 wt. percent SiO besides SnO; and Li O. The effect of combined SnO and Li,0 per se was substantially unaffected when the amounts of addition of CaO and S10 were varied as will be evident from Example 8.

EXAMPLE 8 F 10S. and 16 illustrate respectively graphs of tan Sly and h of manganese-zinc ferrites having a basic composition of 38.0 mol percent MnO, 6.1 mol percent ZnO, and 55.9 mol percent Fe,O and containing from 0 to 0.3 wt. percent CaO and from 0 to 0.04 wt. percent SiO In contrast, FIGS. 17 and 18 illustrate respectively graphs of tan 6/11. and h of these ferrites which contained 0.05 wt. percent U 0 and 1.5 wt. percent SnO, as another additive combination.

It will be apparent from the foregoing examples that a preferred manganese-zinc ferrite composition is provided consisting essentially of about 32.0 to 38.0 mol percent MnO, about 54.4 to 55.9 mol percent Fe O and the balance essentially ZnO, and containing about 0.01 to 0.1 weight percent Li O, about 0.4 to 3.2 weight percent $110,, less than about 0.3 weight percent CaO and less than about 0.04 weight percent S10 A comparison of these graphs readily demonstrates that the effect of addition of SnO, and U 0 per se is still conspicuous under the co-presence of another additive combination C210 and SiO: in varying amounts.

Any of the foregoing examples demonstrates that the addition of small but effective amounts of combined SnO, and U 0 are quite effective for improvements in the loss characteristics of the manganese-zinc ferrites.

The data of the figures together with the small but effective amounts of SnO, and U 0 added to the ferrites are summarized as follows:

Mol FIGS. MnO ZnO Fe,O, wt.% Li,O Wt. i SnO, land 2 38.0 6.10 55.9 0 to 0.1 0.6 to 2.7 3 and 4 36.0 8.8 55.2 0.01 to 0.1 0.6 10 2.7 5 and 6 36 .0 9.5 54.5 0.01 to 0.06 1.0 to 3.2 7 and 8 34.0 11.6 54.4 0 to 0.07 0.810 2.3 9 and 10 34.0 10.75 55.25 0 to 0.06 0 to 1,4 11 and 12 32.0 13.15 54.85 0.01 to 0.05 0.4 to 1.1 13 and 14 38.0 6.10 55.9 0 to 0.08 l to 2.9

Experiments were also conducted to determine the effective limits in amounts of SnO and Li O added to many Mn-Zn ferrite compositions other than those indicted in these examples, covering a wide range as follows: 28 mol MnO 5 4O mol%;51mol% Fe O 58 mol%; balance ZnO. Similar effects due to the addition of SnO and U 0 were observed in such manganese-zinc ferrite compositions. The foregoing has established criteria for markedly improving the magnetic properties in reducing the values of tan 8/ 1. and h to less than 1.3 X 10" and 5, respectively. The small but effective amounts of SnO and U 0 to be added according to these criteria are less than about 3.2 wt. percent and less than 0.125 wt. percent, respectively, for example, from about 0.01 to 0.1 lithium oxide and from about 0.4 to less than 3.2 stannic oxide.

Experimental results have indicted it is difficult to meet these criteria through the addition of SnO- and Li O in instances where the MnO content of the ferrite composition is considerably less than the above-stated minimum MnO content.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and the appended claims.

What is claimed is:

1. A manganese-zinc ferrite composition consisting essentially of about 28 to 40 mol percent MnO, about 51 to 58 mol percent Fe o and the balance essentially ZnO, and further containing less than about 0.3 percent by weight of calcium oxide, and, less than about 0.04 percent by weight of silicon and small but effective amounts of less than about 3.2 percent by weight of stannic oxide and less than about 0.125 percent weight of lithium oxide, said amounts of stannic oxide and lithium oxide being sufficient to effect improvements in the values of the quality factor (tan 6/;/.) and hysteresis loss factor (h of said composition, said ferrite composition being characterized by values of tan 8/;1. at KHz. of less than 1.3 l0' and h at 100 KHz. ofless than 5.

containing about 0.01 to 0.1 weight percent Li O, about 0.4 to 3.2 weight percent SnO less than about 0.3 weight percent CaO and less than about 0.04 weight percent SiO,, said composition being characterized by values of tan Sly. at KHz. ofless than 1.3X10 and h at 100 KHz. ofless than 5.0. 

2. The manganese-zinc ferrite of claim 1, wherein the lithium oxide ranges from about 0.01 to 0.1 percent by weight and wherein the stannic oxide ranges from about 0.4 to less than about 3.2 percent by weight.
 3. A manganese-zinc ferrite composition consisting essentially of about 32.0 to 38.0 mol percent MnO, about 54.4 to 55.9 mol percent Fe2O3 and the balance essentially ZnO, and containing about 0.01 to 0.1 weight percent Li2O, about 0.4 to 3.2 weight percent SnO2, less than about 0.3 weight percent CaO and less than about 0.04 weight percent SiO2, said composition being characterized by values of tan delta / Mu at 100 KHz. of less than 1.3 X 10 6 and h10 at 100 KHz. of less than 5.0. 